October 7, 1897] 



NA rURE 



5^7 



and the book is essentially an argument for it, rather 

 than for natural selection, in support of which as distinct 

 from other suggested agencies it advances comparatively 

 little. 



Its publication naturally aroused Darwin's interest ; 

 he quoted freely from it in the later editions of the 

 " Origin," and arranged for its appearance in an English 

 translation. This was made by Mr. W. S. Dallas, and 

 published in 1869 under the somewhat less forcible title 

 of " Facts and Arguments for Darwin." It materially 

 increased the reputation which Miiller had gained in 

 this country during the preceding twelve years by the 

 appearance m the " Annals and Magazine of Natural 

 History" of translations or abstracts of his chief papers, 

 also from the pen of Mr. Dallas. 



The most important result, however, of " Fiir Darwin " 

 was that it led Darwin to address to Fritz Miiller in 

 August 1865, the first of the long series of letters which 

 passed between the two naturalists. Mr. Francis Darwin 

 has put on record his recollection of the pleasure which 

 his father took in this correspondence, and his im- 

 pression that of all unseen friends Miiller was the one 

 for whom his father had the strongest regard. Closely 

 in touch with nature as Miiller was, his was exactly the 

 adherence which was most welcome to Darwin, who so 

 directly recognised the affinity in character and mental 

 outlook between himself and his correspondent that, in 

 asking for Mijilers opinion on pangenesis, he wrote : " I 

 value your opinion more than that of almost any one. . . 

 I feel sure that our minds are somewhat alike." 



Some of the letters written by Miiller were sent for 

 publication to Nature ; from these as well as from 

 the references in Darwin's published correspondence and 

 books, particularly " The Forms of Flowers " and "• Cross 

 and Self- Fertilisation of Plants," some idea can be formed 

 of the abundance of new and interesting observations on 

 all sorts of subjects, largely botanical, which Miiller made 

 and communicated. These letters, which drew from 

 Darwin the exclamation : " Heaven knows whether I 

 shall ever live to make use of half the valuable facts 

 which you have communicated to me," show, even better 

 than his papers, Miiller's insight into and sympathy with 

 Darwin's work, and his consequent tendency to be al- 

 ways on the look-out for any peculiarity of structure or 

 habits that could be interpreted by natural selection. 



Thus, when in the controversy as to the existence of 

 the insect required, ex hypothesis to reach the nectary of 

 AngrcEcutii, it was contended that no existing moth pos- 

 sessed a proboscis of the necessary length— about 

 eleven inches — Miiller entirely disposed of the contention 

 by forwarding the proboscis belonging to an unde- 

 termined Brazilian Sphinx, of the length required, to his 

 brother, who described and figured it in these columns. 



In 1867 the increasing influence of the Jesuits com- 

 pelled Miiller to leave Desterro, and he returned to the 

 occupation of a farmer, a change which brought his work 

 on marine zoology to an end. At this time he was ap- 

 pointed naturalist to the Brazilian Government, and 

 somewhat modified the range of his studies, occupying 

 himself with entomology and botany, and applying a 

 more systematic attention to bionomics and field ob- 

 servation. Although often looked upon as mainly an 

 entomologist, he published nothing on insects during the 

 first thirty years of his career. In 1873, however, he 

 began a series of papers on Termites in the Jenaische 

 Zeitschrift ; these contain some of his most brilliant con- 

 ceptions in the theories put forward as to the existence 

 and function of the supplementary reproductive forms and 

 the uselessness of the true imagos, as well as in the com- 

 parison of the two kinds with cleistogamic and perfect 

 flowers. Although the facts at his disposal were in- 

 sufficient to enable him to confirm his theories, they 

 formed the foundation on which Prof. Grassi has since 

 successfully built, and which he has appropriately 



NO. 1458, VOL. 56] 



acknowledged by the dedication of his monograph to his 

 predecessor. 



F'ritz Miiller's most familiar entomological work is 

 certainly that on mimicry. The original theory of Bates 

 failed to suggest any explanation of the most striking 

 class of resemblances found among butterflies, those 

 subsisting between pairs or among groups of what are 

 regarded as protected forms, and was open to criticism 

 on several points for want of evidence. Bates, it must 

 be recollected, did not elaborate it on the Amazons, but 

 after his return to England, when all opportunity of 

 specially directed observation had ceased for him. 

 Miiller first dealt with the possibility of the origin by 

 gradual stages of a mimetic from a non-mimetic pattern, 

 a point left so little treated as to have invited scepticism ; 

 but his work, though sound in principle, suffered from a 

 want of familiarity with the range of form in the genera 

 discussed, which only the resources of a museum could 

 remedy, and the idea has been recently worked out more 

 exhaustively by Dr. Dixey. 



In 1879 Miiller published in " Kosmos," to which he 

 had been a regular contributor from the first, the well- 

 known hypothesis framed to supplement that of Bates^ 

 and based on the assumption that a bird learns to recog- 

 nise and avoid an unpalatable species of butterfly as the 

 outcome of a series of experiments. The toll thus taken 

 must stand in relation to the number of birds and not of 

 butterflies, and would therefore be distributed over two 

 or more species of the latter by their acquisition of a 

 common appearance, a fraction only of the loss falling 

 on each component of such a group. 



The " Miillerian theory," though destined to perpetuate 

 its author's name, is scarcely typical of his work in so 

 far as it is an ingenious speculation, not dependent on 

 direct observation, but one which could have been evolved 

 by a naturalist who had never seen a living example of 

 the insects it deals with. Still, it remains the first and 

 only serious attempt to bring an intractable class of facts 

 within the scope of natural selection, and, even if it 

 should be ultimately superseded, it will have immensely 

 advanced the study of these wonderful resemblances. 



The paper containing Miiller's article was sent by 

 Darwin to Prof. Meldola, then Secretary of the Ento- 

 mological Society of London, who recognised its import- 

 ance, and at once published a translation. The theory, 

 however, met with much opposition, including that of 

 Bates himself, then somewhat past the reception of new 

 ideas, but to its authors great gratification it found a 

 warm supporter in Dr. Wallace, whose adhesion involved 

 the abandonment of an earlier view that these resem- 

 blances were due to unknown local conditions. Three 

 years later this view was strenuously combated by 

 Miiller in an important but untranslated, and therefore 

 less familiar, article. To accept its main argument, that 

 these likenesses result from some process of visual selec- 

 tion — and it has never been seriously answered — does 

 not compel belief in a destructive process. Though 

 Miiller suggests no alternative in his paper, he appears- 

 to have held and privately put forward the idea that 

 another factor, that of direct selection or segregation on 

 the part of the insects themselves, might play some part. 

 He paid a large amount of attention to the scent-tufts,, 

 odours and other means of recognition in butterflies, and 

 at a somewhat earlier period had so far expressed his 

 views that we find Darwin writing to him in 1871 (" Life 

 and Letters of Charles Darwin," iii. p. 151) : "Would you 

 object to my giving some such sentence as follows : ' Y^ 

 Miiller susptcts that sexual selection may have come into 

 play, in aid of protective imitation, in a very peculiar 

 manner, which will appear extremely improbable to 

 those who do not fully believe in sexual selection. It is 

 that the appreciation of certain colour is developed in 

 those species which frequently behold other species thus 

 ornamented.'" Granted that this was a somewhat 



